Cancer progression depends on the action of proteolytic systems that facilitate the growth and invasion of tumor cells. The membrane type-1 matrix metalloproteinase (MT1-MMP) endows tumor cells with the ability to invade and grow within collagenous matrices and thus is a key protease in cancer progression. As a membrane-tethered protease, MT1-MMP is regulated by a dynamic interplay of regulatory mechanisms that collectively control the level of active enzyme on the tumor cell surface and in the pericellular space. The long term objective of this application is to unveil the mechanisms regulating MT1-MMP activity at the tumor cell surface and apply this knowledge towards the development of new approaches aimed at inhibiting MT1-MMP in cancer. Our previous effort has been focused on elucidating the structural features and biochemical processes that define the ability of MT1-MMP to undergo autocatalytic processing and ectodomain shedding on the cell membrane, two fundamental processes of enzyme regulation. Processing of active MT1-MMP yields an inactive membrane-tethered fragment of 44 kDa that maintains key enzyme domains but its function in MT1-MMP regulation is poorly understood. Ectodomain shedding of MT1-MMP yields a 50-kDa soluble form that is present in tumors and is a fully competent protease. However its contribution to tumor proteolysis is unknown. Herein, new evidence in vitro and in tumor xenografts shows that the membrane-tethered 44-kDa species, displays a dynamic interaction with active MT1-MMP and identifies this fragment as a complex regulator of enzyme function in tumor cells. The naturally shed ectodomain of MT1-MMP has been characterized and found to be a catalytically competent protease, sensitive to TIMP-2, which has the potential to expand the proteolytic repertoire of MT1-MMP from the confines of the cell membrane to the pericellular space and regulate the activity of membrane-anchored MT1-MMP. Collectively, these observations pose a new paradigm in the regulation of MT1-MMP activity and suggest the hypothesis that processed and soluble forms of MT1-MMP play critical roles in tumor malignancy. To test this hypothesis we propose to: (1) investigate the dynamic interplay between the processed and active forms of MT1-MMP in enzyme function, (2) define the structural basis for the effects of the 44-kDa species on MT1-MMP regulation, (3) investigate the role of the soluble MT1-MMP in the regulation of MT1-MMP activity and (4) investigate the role of processed and soluble forms of MT1-MMP in functional assays of tumor cell invasion and growth in vitro and in vivo. The results of this application will contribute to our understanding of MT1-MMP function in tumor cells and contribute to the collective effort aimed at inhibiting its activity in cancerous tissues. PERFORMANCE S\"TE(S)(organization, city, state) Wayne State University Detroit Ml PHS 398 (Rev. 09/04) Page _2 Form Page 2 Principal Investigator/ProgramDirector (Last, First, Middle): FridmaD, Rafael A KEY PERSONNEL. See instructions. Use continuation pages as needed to provide the required information in the format shown below. Start with Principal Investigator. List all other key personnel in alphabetical order, last name first. Name eRA Commons User Name Organization Role on Project Fridman, Rafael RFRIDMAN Wayne State University PI OTHER SIGNIFICANT CONTRIBUTORS Name Organization . Role on Project Schuger, Lucia Wayne State University Consultant Shisheva, Assia Wayne State University Consultant Human Embryonic Stem Cells ^ No FJ yes If the proposed project Involves human embryonic stem cells, list below the registration number of the specific cell line(s) from the following list: http://stemcells.nih.gov/reqistrv/index.asp. Use continuation pages as needed. If a specific line cannot be referenced at this time, include a statement that one from the Registry will be used. Cell Line Disclosure Permission Statement. Applicable to SBIR/STTR Only. SeeSBIR/STTR instructions. FJ Yes FJ No PHS 398 (Rev.09/04) Page 3 Form Page 2-continued Number the following pages consecutively throughout the application. Do not use suffixes such as 4a, 4b. Principal Investigator/Program Director (Last, First, Middle): Fridman, Rafael The name of the principal investigator/program director must be provided at the top of each printed page and each continuation page. RESEARCH GRANT TABLE OF CONTENTS Page Numbers Face Page 1_ Description,